Lepto-axiogenesis and the scale of supersymmetry

TL;DR

This paper explores how early universe rotations of the Peccei-Quinn field can generate the baryon asymmetry through lepto-axiogenesis, linking it to supersymmetry scales and axion dark matter production.

Contribution

It provides a detailed computation of lepto-axiogenesis efficiency in supersymmetric axion models and establishes bounds on superpartner masses based on baryon asymmetry.

Findings

Efficiency of asymmetry generation is increased in KSVZ model with superpartners.

Superpartner mass bounds are around 30 TeV for KSVZ and DFSZ models.

Possible upper bounds on superpartner masses are around PeV when considering axion dark matter.

Abstract

If the Peccei-Quinn field containing the QCD axion undergoes rotations in the early universe, the dimension-five operator responsible for neutrino masses can generate a lepton asymmetry that ultimately gives rise to the observed baryon asymmetry of the Universe. This lepto-axiogenesis scenario requires a flat potential for the radial direction of the Peccei-Quinn field, naturally realized in supersymmetric models. We carefully compute the efficiency of this mechanism for the Dine-Fischler-Srednicki-Zhitnitsky (DFSZ) and Kim-Shifman-Vainshtein-Zakharov (KSVZ) axion models and place lower bounds on the masses of scalar superpartners required to reproduce the observed baryon asymmetry. For the KSVZ model, we find an efficiency for generation of the asymmetry six times larger than the previously extant computation after including scattering channels involving superpartners. In this case, the superpartner scale should be above $\sim$ 30 TeV for a domain wall number of one; the lower bound weakens for larger domain wall numbers. We find that the superpartner mass scale may also be as low as 30 TeV for the DFSZ model. In all cases, the lower bound on the superpartner masses is inversely proportional to the sum of the squares of the neutrino masses and so can strengthen as the upper bound on the neutrino mass improves. We identify the parameter space where the axion rotation can simultaneously produce axion dark matter via kinetic misalignment; in this case it is possible to put an upper bound of order PeV on the masses of scalar superpartners.